Re: E.6.3.2.1. Constraints

> My question here is whether error code changes are incompatibilities
> worthy of being mentioned in the release notes, and if committers
> don't mention this in the commit message, how would I find them when
> creating the release notes?

The 18 notes already list one SQLSTATE change, cd838e200 for XML
errors, so leaving out 086c84b23 makes them inconsistent: both change
what code an application gets for the same error.

I can see why it was missed, though. The commit message presents it
as following the standard rather than as a behavior change, and
nothing in errcodes.txt changed: cd838e200 added new codes there,
while 086c84b23 started using 23001, which had been defined but unused
since 2003 (7.4).

So I think it belongs next to cd838e200 in the version 18 notes (it
went into 18.0, not 19). The general question is a good one for
hackers, but could this case be handled on its own?